An analysis of the general case is, however, considerably more difficult and has remained elusive until the recent proof of commutator scaling of Trotter error [1]}. Here, we introduce a stronger version of that result which can be proved as in [2]} by combining Theorem 3, 4, and 5 of [1]} without invoking the triangle inequality.It is essential to invoke a representation of the Trotter error where nested commutators have at most a constant number of layers [1]}. If such a representation were not used, Trotterization would have a worse asymptotic complexity [5]}.
